<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>多类名引用</title>
    <style>
        .box {
            width: 150px;
            height: 100px;
        }
        
        .font35 {
            font-size: 35px;
        }
        
        .red {
            background-color: red;
        }
        
        .green {
            background-color: green;
        }
    </style>
</head>

<body>
    <p class="red font35">我</p>
    <div class="red box">红色</div>
    <div class="green box">绿色</div>
    <div class="red box">红色</div>

</body>

</html>